The invention concerns a method for producing a resistive heating element by coating a substrate with an electrically insulating material from the gaseous phase, depositing an electrically conducting material from the gaseous phase onto the layer of insulating material deposited onto the substrate, and subsequent mechanical removal of at least parts of the layer of a conductive material deposited onto the layer of insulating material thereby forming at least one conductor path. The invention also concerns a resistive heating element comprising a substrate onto which an electrically insulating layer is disposed, with an electrically conducting layer in the form of at least one conductor path being disposed onto the insulating layer.
Resistive heating elements of this type are conventionally used in various applications, in particular as heaters. They are produced by coating a usually plate-shaped substrate, e.g. of graphite, with an electrically insulating material, generally having a maximum layer thickness in the mm region. A further layer of an electrically conducting material is then deposited onto the layer of insulating material disposed on the substrate, wherein the layer thickness of the conducting material is adjusted in dependence on the desired electrical resistance. The layers are normally applied using chemical vapor deposition. When the conducting layer has been applied, it must be mechanically removed in parts to form an e.g. meandering conductor path. An electrical voltage is applied to the ends of the conductor path for operating the resistive heating element.
The mechanical processing of the flat conducting layer requires an excessive amount of time and expense and, in particular, requires high precision with tolerances of better than 0.01 mm, since short-circuits in the generated conductor path must be prevented and therefore the layer of conducting material between the regions which form the conductor path and which remain on the insulating layer must be completely removed. On the other hand, the insulating layer disposed below the layer of conducting material must not be impaired to prevent short-cuts. Moreover, layers which are, in particular, disposed onto relatively large-surface substrates through chemical vapor deposition have a varying thickness within their overall surface and must be mechanically finished to produce a constant conductor path thickness along its entire length. This renders processing more difficult.
It is therefore the underlying purpose of the invention to propose a simple and inexpensive method for producing a resistive heating element of the above-mentioned type thereby avoiding the above-mentioned disadvantages. The invention also concerns a resistive heating element which is produced by such a method.